The invention relates generally to self-propelled earth or rock drilling machines having a retractable mount for the power driven turntable or rotary drive for the drill pipes which is applicable for drilling anchoring bore holes on construction sites or for drilling blast holes in quarries.
From prior art drilling machines of this kind are known which are equipped either with a relatively short mount for the turntable which may be provided with a storage compartment for drill pipes and is movably supported on a cantilever beam whereby upon drilling a bore hole about the length of one drill pipe an extension drill pipe has to be added; in a modification, a drilling mast is pivotably supported on a platform of a self-propelled undercarriage and can be erected or retracted by means of a supporting cylinder. The above-described known drilling machines are described for example in the brochures WO26.779.1500 P, W275.679.500 A and W386.678.1000 G of the German firm Salzgitter Maschinen und Anlagen AG.
In the latter embodiment of the known drilling machine, it is possible to drill a hole over the entire length of the mast without the necessity of extending the drill pipes. The permissible length of the mast depends on the total weight of the machine inasmuch as during the movement from one drilling site to another one with erected mast, it is necessary to ensure that the mobile machine does not overturn even if moved on a rough surface. The retraction of the mast before the transport, however, has the disadvantage that a considerable part of the mast overhangs the undercarriage. Moreover, the structure of the mast must be very stable because in the horizontal or in an inclined position the mast is subject to a large bending moment in the range of the supporting points because of the increased cantilever load.
The disadvantage of the first mentioned embodiment of the known drilling machines is to be seen in the fact that due to the necessity to extend the drill string considerable wasted time results and furthermore the provision of a storage compartment for the drill pipes makes the machine more expensive and susceptible to failures. In the second embodiment of the known machines, the total weight of the rig is very high and this in turn leads to higher costs. In addition, the maximum length of the drilling mast is limited presently to about 10 to 15 meters which length is unfavorably small.